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vermiculite installation

04-14-2010, 12:35 PM

I am planning on starting my pizza oven in a couple of weeks and need a little help. It is best to pour vermiculite insulation first or is it best to pour concrete first? I have read several articles and from what I have read it can be either way. I have never seen vermiculite installation firsthand, it appears to have a very rough surface of the photos that Iíve seen. If so do you have a trouble getting the cooking floor level? I would appreciate help that you can give me.

The concern that has been raised on FB is the general irrationality of placing a concrete slab on top of the insulating layer. The consequence is that heat radiating through the oven floor will continue to radiate through the concrete before reaching the insulation, thus resulting in tremendous heat loss.

The general wisdom on leveling the vermicrete in prep for the floor is to coat it with fireclay and rake it down smoothly. I can't comment on this at all since I didn't use vermicrete for my floor insulation. I have no idea what would be involved in leveling or otherwise flooring on a vermicrete slab...but lots of people have done it successfully.

Comment

I too have asked this question and after many responses AND additional research on my part here is what you should do.

The vermiculite or perlite insulation concrete should go on top of the hearth and under the oven fire brick floor. The main reason for this is due to the heat sink or more simply put the amount of time it would take to heat up your oven to pizza cooking tempertures.

The builds you have seen with the perlite concrete under the hearth I belive comes from the book and advice provided by a gentleman by the name of Alan Scott. The ovens he designs are mainly for bread baking. Although you can get up to the higher tempertures it takes much longer due to the large amount of mass you will be heating. The advantage of his ovens is the fact that this large mass will maintain the heat for a longer period of time. This will allow you to bake numerous batches of bread which is good for commerical operations.

Unless you plan on going in the bread baking business I would think that the following the advice on this forum would be better, since the pizza oven design will allow you to also bake bread but probably not the 6-7+ batches that all that heated mass would allow.

Keep in mind that when I say batches that is not loaves! Each batch can contain as many loaves that you can fit in the oven.

Comment

One other thing I failed to mention about the perlite concrete. This is also called Light weight concrete in the industry. It is used in insustries where there is the potential of exposure to accidental spills of cryogentic liquides (LNG, N2 et

c) This protects the underlay and retards some of the flashing of the cryogentic liquid. As far as the surface finish most of the photos you have seen I believe is due to the consistance or the amount of water that is added to the perlite concrete. It will level just like any concrete and it can be worked a bit to smooth out the surface appearence.

Do not confuse the surface finish with level. don't forget in all cases it is recomended that you place a fireclay/sand leveling course down and trowel it like you are lay tile adheasive, under the oven floor.